Diesel fuel



I Patented June 27, 1939 'acteristic that is highly desirable.

combustion takes place.

tion, the 'low compression pressure permits of a g T UNITED STATES PATENT OFFICE DIESEL FUEL No Drawing. Application October 29, 1937,

' Serial No. 171,670-

7 Claims.

This invention has to do in a general way with fuels for internal combustion engines of the Diesel type and is more particularly concerned with the modification of such fuels by the addition of characterizing ingredients for the purpose of modifying or controlling the combustion characteristics.

In the Diesel cycle internal combustion engine where thefuel is injected into a combustion space it is important, to the attainment of' maximum efiiciency, that the delay period between injection and ignition be short. It will thus be seen that enhanced speed of ignition is a char- Improperly delayed ignition in a Diesel engine gives rise to the phenomena known as knocking, due to improper coordination of combustion and cylinder conditions. By accelerating the ignition of Diesel fuel it is possible to lower the compression pres-' sure which will insure spontaneous ignition without combustion shock, thereby increasing the ease of starting and the smoothness with which In this same conneclower weight in the engine and a lower cost per given power output.

It has been found that the ignition quality of a fuel oil can be improved by the addition-of small amounts of certain compounds which act as ignition accelerators. This offers a means for improving the better grades of Diesel fuels and a means of widening the range of available fuels by raising the ignition quality of lower grades to a point where they can be satisfactorilyused.

A number of compounds have been proposed as ignition accelerators for Diesel fuels. Among such compounds are such materials as ethyl nitrate, alkyl nitrites, and certain peroxides.

Many of these compounds are unsatisfactory from the standpoint of stability, cost, or toxicity.

Our present invention is directed to Diesel type fuels which have been improved in ignition quality bythe addition of novel compounds which promote rapidity of combustion and so give the desired control to the combustion characteristics of the fuel. I I

By. the term Diesel type fuels" or "Diesel fuel" as it is used herein we have reference. not only to the distillates' of the kerosene-like boiling range commonly denoted as Diesel fuel, but we intend to include, as well; the general field of hydrocarbon products, both heavier and lighter than the fuel above referred to, such, for example, as the light and heavy fuel oils and gasoline for use in.Diesel cycle engines.

The present invention is directed to a method for improving the ignition quality of Diesel fuel and a fuel which has been improved by the addition to a. base fuel stock in minor proportions of a novel ignition accelerating ingredient. The particular class of additive ingredients contemplated by this invention are compounds of the type which may be obtained by the interaction of an aryl amine with elementary sulfur and have the general formula,

in which B. may be hydrogen or an alkyl group, R is an aryl group, and n is a whole number from 1-3 inclusive.

More specifically, the particular compounds of the general type which we have demonstrated as having ignition accelerating value when added to Diesel fuel, are the reaction products of phenyl amines and elementary sulfur which have the general formula,

In this formula R may a hydrogen or an alkyl group (such as methyl, ethyl, butyl, or amyl), the group 4 c rresponding to an aniline residue, a nitrogensubstituted aniline residue, 2. carbon-substituted aniline residue, or a nitrogen-substituted and carhon-substituted aniline residue. The letter 11.

, represents a whole number from 1-3. These bis (amino. aryl) sulfides are unsaturated compounds of sulfur.

Compounds of the general type last above referred to can be conveniently prepared by the interaction of an aniline compound and elementary sulfur. Thus aniline disulfide can be prepared by the interaction of aniline and sulfur with the elimination of hydrogen sulfide according to the following reaction:

(Hodgson,

2,2 diamino diphenyl disulflde, and while this isomer is initially produced in the reaction, the isomer 4,4 diamino diphenyl disulfide is formed in increasing amount as the temperature rises.

The unreacted aniline is removed by steam distillation. Theaniline-sulfur complex is removed from the unreacted sulfur by converting the'former to its hydrochloride and extracting this with hot water. The hydrochloride salt extract then yields the free aniline-sulfur complex when neutralized with a base such as. caustic soda.

The aniline-sulfur complex thus obtained consists mainly of a mixture of isomeric aniline disulfides. The crude product melts at 72-84 C. When pure, the isomer, 2,2-diamino diphenyl disulfide,'melts at 93 C. (Mohlau, Beyschlag and Kohres, Ber. 45, 133 (1912); the 3,3'-diamino diphenyl disulfide melts at 59-60 C. (Fichter and Tamm, Ber. 43, 3037, (1910); and the 4,4'-diamino diphenyl disulfide melts at 81-82" C. (Leuckert and Lustig, J. Prakt. Chem. (2), 41, 204, (1890).)

In our work the crude product melting at 72-84 C. was found to be effective, and the term aniline disulflde as used herein is intended to include this product.

Inconducting the tests which have demonstrated the value of compounds belonging to the general class contemplated by this invention as ingredients for improving Diesel fuels, we have determined the ignition quality of the blended fuels by comparison with standard reference fuels in a converted CFRengine, using the ignition delay method. The results of these tests are expressed by cetane numbers. number is the per cent by volume of cetane in a blend of cetane and alpha-methylnaphthalene, which blended fuel has the same combustion characteristics as the sample being tested. (Proc. Am. Soc. Testing Materials vol. 36, I 'p. 418.) An increase in cetane number indicates a decrease in delay between fuel injection and fuel ignition, and consequently indicates an improvement in fuel combustion characteristics.

As an example of the improved ignition quality obtained through the use of compounds of the general type contemplated by this invention, we

, have indicated inthe table below, the results of tests conducted along the lines outlined above. The value of the additive .ingredients contemplated by the present invention is shown by the octane number of the unblended base stock was 42.0.

ass: 00916 The cetane Bis' (aminoaryl) sulfide compounds of the type illustrated in the foregoing examples may be used in varying amounts depending upon the base fuel stock and the extent to which it is desired to improve its ignition quality or decrease the ignition delay period. They may be used in proportions up to complete saturation of the fuel, but in general lower concentrations are preferred, and a concentration in the neighborhood of 0.5% is believed to be sufiicient for ordinary purposes.

In the foregoing specification and in the following claims, the terms Diesel fuel, hydrocarbon fuel oil, etc., include any and all types of hydrocarbon products intended for use in an engine operating according to the Diesel cycle.

We claim:

1. An improved Diesel fuel comprising: hydrocarbon fuel oil and in admixture therewith a minor proportion of a bis (aminoaryl) disulfide.

2. An improved Diesel fuel comprising: hydrocarbon fuel oil and in admixture therewith a minor proportion of a diamino diphenyl disulfide, suflicient to decrease the ignition delay period of the fuel.

3. An improved Diesel fuel comprising: hydrocarbon fuel oil and in admixture therewith a minor proportion of a o-toluidine disulfide, suflicient to decrease the ignition delay period of the fuel.

4, An improved Diesel fuel comprising: hydrocarbon fuel oil and in admixture therewith a minor proportion of an aniline disulfide, suflicient to decrease the ignition delay period of the fuel.

5. An improved. Diesel fuel having admixed therewith, in suilicient amount to decrease the ignition delay period of the fuel, a minor proportion of a compound having the probable formula the group corresponding to an aniline residue in which R may be hydrogen or an alkyl group.

6. The method of accelerating the ignition of liquid fuels for internal combustion engines of the type wherein ignition of the fuel is spontaneously effected by injection into the compressed air in the engine cylinder, which comprises admixing with the fuel, prior to ignition a minor proportion-of a diamino diphenyl disulfide.

'l. The method of accelerating the ignition of liquid fuels for internal combustion engines of the type wherein ignition of the fuel is spontaneously effected by injection into the compressed air in the engine cylinder, which comprises admixing with the fuel, prior to ignition a minor proportion of a compound having the probable formula in which B may be hydrogen or an alLvl group and R is an aryl group.

GEORGE S. CRANDALL.

WILLIAM H. JAMES, 

